[small.planes]

hi all,
Im considering a new CNC build (I have a Proxxon MF70 based conversion).
I want something a little larger, I have a honking big manual mill (11"x49" TOS) so somewhere between the 2.
I think the travels on the X3 are about what Im looking for (~5.5"x14").
However the Super X1L is not far short in the travels dept (~1.2" in the X and a shorter Z), and is considerably cheaper. (approx 1/3 price)
Given that Im going to CNC it, and hence effectively the mill is a kit of approximately correct shaped castings is there a good (£400) reason to choose the X3 as a starting point?

(there will of course be more questions once I start :wee: )

cheers

Dave

[acondit]

Yes, its rigidity. I have an X2 and neither an X1 or X3, so I am reporting what I have read not what I know. I believe the X3 has a better spindle setup as well as a more rigid column than the X1. But ultimately its your money, and your choice.

Alan

[slashmaster]

I have an X3. It originally got 16"x, 5 3/4"y and 14 3/4"z. I cut material off the table endplates so now I get 20 1/2"x and could easily get another 1/2" of z if I jack up the electronics cover on back. This mill has reverse so you can tap threads too, I don't know if a sx1l is like that.

You have me confused, you say you have a small mill and a honking big 11" by 49" manual mill already right? Why would you ever need another? Why not just cnc your big mill.

[small.planes]

Ok, maybe small is a bit to large a word for the proxxon, Travel is 134 mm (x axis), 46 mm on the y axis, Z (height) 80 mm. so tiny might be better.
It is my first foray into CNC, and its easy to find space for it. unfortunatly it is really to small for the next project I have, and although I could do it on the manual mill I think it would be a good CNC job (identical sets of bits for an engine, eg 4 con rods)

I dont really want to CNC my big mill, I quite like using it and it would need a lot of work (big heavy bits, very large motors etc). Theres always a need for another machine

guess I need to look in the flesh at the machines, I thought the X3 column was mostly a sheet metal part that didnt really add anything.

Dave

[hoss2006]

I have a pic on my mill comparison page that could give slash an idea of what you have now.
A Proxon on a kneemill.


The X3 would make a good intermediate.
Hoss

[acondit]

Ok, maybe small is a bit to large a word for the proxxon, Travel is 134 mm (x axis), 46 mm on the y axis, Z (height) 80 mm. so tiny might be better.
It is my first foray into CNC, and its easy to find space for it. unfortunatly it is really to small for the next project I have, and although I could do it on the manual mill I think it would be a good CNC job (identical sets of bits for an engine, eg 4 con rods)

I dont really want to CNC my big mill, I quite like using it and it would need a lot of work (big heavy bits, very large motors etc). Theres always a need for another machine

guess I need to look in the flesh at the machines, I thought the X3 column was mostly a sheet metal part that didnt really add anything.

Dave

No, it is a good cast iron column with some sheet metal coverings.

Alan

[small.planes]

Hoss, funny what turns up, thats actually my proxxon on my TOS FNK25

Had a quick look at an X3 this evening, yep its quite a bit beefier than an X1 in the column area, and also the table/saddle looks stronger.

guess I need to get a larger budget approval from SWMBO


Dave

[hoss2006]

No kidding?
That's funny, I saw that pic on the Home Shop Machinist forum a long time ago.
Small world.
Hoss

[slashmaster]

Hoss, funny what turns up, thats actually my proxxon on my TOS FNK25

Had a quick look at an X3 this evening, yep its quite a bit beefier than an X1 in the column area, and also the table/saddle looks stronger.

guess I need to get a larger budget approval from SWMBO


Dave

Oh yeah, the column is heavy! I took my mill apart to get it in my basement, I seperated it into Base, saddle, table, column, head, motor and electronics cover. I just barely carried the column into the basement with the leadscrew, nut and its plate still attached, next time I'm taking those pieces off too. I'm thinking about doing the same thing Hoss did and seeing how well my column fits in the saddle. It is 29 1/8" long.

By the way, looks like you already have great equipment now! Are you starting a mill collection or something? Is the TOS FNK25 really your dads and he would be pissed if you cnc it? Or is it worth a lot as an antique and you don't want to mutilate it by drilling holes in it for steppers?

[small.planes]

nope, it really is mine. Its not an antique (well 1988), and it *could* be CNC'd I guess, but not this time (Its to heavy to move around and its set into a corner so it doesnt eat *all* the workshop space. )
A picture of my workshop:

Behind me is a wall and a surface grinder TIG set and 'dirty work area'.

A bit of background:
A couple of years ago I was making a lot of small parts for sub micro helicopters (about 15mmx5mmx1.6mm) using the TOS.
I decided that this was a bit silly and the proxxon would fit the bill better for tiny parts (20K spindle for a start), but it took longer to convert than intended, and now I dont make those parts any more.
Now the Proxxon is ok for tiny, but the next project lined up is a 999cc 4pot turbo, and I need to do some engine sized bits (crank, conrods etc). I could do them on the TOS, but any excuse to get a new toy
The TOS is a nice to use manual machine, and for one offs and such it saves having to draw/gcode things. Its also a Knee mill, and as such I think Id need to have both the quill and the knee cnc'd, which when you add a RT means 5 (4 stonking big) drivers.
So as a relative noob to the CNC world I figured a larger useful benchtop size machine to play and learn on would be a good thing. (cheaper crashes :drowning: )

Having seen a lot of X series conversions that seems like a good place to start, knowledge available already. I think that I might roller nut all the axis (trying to do this on a budget, but if I have to remake the stock nuts anyway...) and generally consider the mill as a shipped together kit that needs assembling...

cheers

Dave

[slashmaster]

Interesting shop. That mill looked a lot older than 88. Is the Lathe the same vintage? Why would you cnc the knee and the quil? I've never heard of anyone doing that. An X3 also has a quil ya know.

[small.planes]

Lathe is about 1955 vintage, Harrison L5

Quill has only about 5" of travel, whereas the knee has more, I assumed that you would CNC all the moving functions. I am a begginer at this.
For a benchtop mill Id only do the head I think, as the quill is not very rigid when out and unlocked? And the Quill and head move together anyway.
The TOS quill is, but thats a monster industrial mill.

Dave

[wildwestpat]

Hi Dave

I am a few steps ahead of you in the building of a small cnc mill. As others have pointed out rigidity is the goal and makes a useful yard-stick for making your choice once you have decided on the XY&Z travels that you need.

After a lot of searching on the web for information on the various choices I decided that any mill with a round column or a quill was not going to deliver for similar reasons. The problem with achieving rigidity with a single round shaft is going to be difficult if a reasonable axis feed is going to be achieved. The mills that use the single round column and or a quill are designed to make plunging cuts and do not readily support the horizontal pressures induced by milling without locking the quill and or column. Whilst the locking and unlocking of the quill and or column could be automated the control would interrupt any 3D tool path. It is for this reason I ruled out a number of other wise very attractive manual mills. I then found the Redbull machines which are available in the UK from Amerdale and Bigdog in the US. After a lot of debate I bought a CJ12 (CJ9512) which has gib adjustable slide ways for all axis. The standard machine achieves 140 mm y axis 320mm X axis and 210mm Z axis movement.

My goal is to get the three axis fitted with ball screws although the screws fitted are smooth and the backlash is reasonable. I have the drawings done for the parts and have at last accumulated the metal to make all the bits. Screws are from Marchantdice 16mm. The design has taken me some time as I want to avoid cutting into the castings of the frame other than the odd small drill hole. My fear is that the castings may be under stressed and that these stresses could cause the casting to warp after cutting anything other than a small hole. (By way of history normal workshop practice is to rough machine castings and then leaves them for a few days or heat treat them before final finishing to size. Obviously we don’t know if this is carried out in the Oriental factories where most of the machines come from.) Incidentally there are a number of different factories involved in making small mills in the Far East as well as similar ones bearing different badges from the same factory.

Suggest you investigate some of the later offerings from Amerdale as you are in the UK . If you contact them you will I am sure get good advice on the differences.

The main differences between the Sieg X2 and the Redbull CJ12 are in the thickness of the castings. For example the base casting where the flanges extend the whole length of the machine and the Z axis mast where the casting is closed in all faces with the exception of two small apertures on the back face towards the top of the mast.

If you are in the SE England a visit to Amerdale London E11 and possibly to WARCO in Surrey would help clear up a lot of the finer points on rigidity. There is nothing like applying a bit of sideways grunt to the axis to see if they move!

Good luck – once you have decided just go for it. Now I have retired I hope to start cutting metal soon if I can get ahead of the domestic painting chore.

[slashmaster]

I totally understand everything about a round column being a bad thing but you're saying a square column with a quil is bad too? Even if it is locked tight all the way up in the spindle? This is the first time I ever heard of people roughing a part and ultimately getting better results if they leave it a few days before they finish it. Can you tell more about that please?

Hi Dave

I am a few steps ahead of you in the building of a small cnc mill. As others have pointed out rigidity is the goal and makes a useful yard-stick for making your choice once you have decided on the XY&Z travels that you need.

After a lot of searching on the web for information on the various choices I decided that any mill with a round column or a quill was not going to deliver for similar reasons. The problem with achieving rigidity with a single round shaft is going to be difficult if a reasonable axis feed is going to be achieved. The mills that use the single round column and or a quill are designed to make plunging cuts and do not readily support the horizontal pressures induced by milling without locking the quill and or column. Whilst the locking and unlocking of the quill and or column could be automated the control would interrupt any 3D tool path. It is for this reason I ruled out a number of other wise very attractive manual mills. I then found the Redbull machines which are available in the UK from Amerdale and Bigdog in the US. After a lot of debate I bought a CJ12 (CJ9512) which has gib adjustable slide ways for all axis. The standard machine achieves 140 mm y axis 320mm X axis and 210mm Z axis movement.

My goal is to get the three axis fitted with ball screws although the screws fitted are smooth and the backlash is reasonable. I have the drawings done for the parts and have at last accumulated the metal to make all the bits. Screws are from Marchantdice 16mm. The design has taken me some time as I want to avoid cutting into the castings of the frame other than the odd small drill hole. My fear is that the castings may be under stressed and that these stresses could cause the casting to warp after cutting anything other than a small hole. (By way of history normal workshop practice is to rough machine castings and then leaves them for a few days or heat treat them before final finishing to size. Obviously we don’t know if this is carried out in the Oriental factories where most of the machines come from.) Incidentally there are a number of different factories involved in making small mills in the Far East as well as similar ones bearing different badges from the same factory.

Suggest you investigate some of the later offerings from Amerdale as you are in the UK . If you contact them you will I am sure get good advice on the differences.

The main differences between the Sieg X2 and the Redbull CJ12 are in the thickness of the castings. For example the base casting where the flanges extend the whole length of the machine and the Z axis mast where the casting is closed in all faces with the exception of two small apertures on the back face towards the top of the mast.

If you are in the SE England a visit to Amerdale London E11 and possibly to WARCO in Surrey would help clear up a lot of the finer points on rigidity. There is nothing like applying a bit of sideways grunt to the axis to see if they move!

Good luck – once you have decided just go for it. Now I have retired I hope to start cutting metal soon if I can get ahead of the domestic painting chore.

[mwood3]

By way of history normal workshop practice is to rough machine castings and then leaves them for a few days or heat treat them before final finishing to size.

Ive never hear of this practice either, im interested...

[wildwestpat]

Hi folks

To amplify further on the old fashined and I believe correct way to machine iron castings as this appears to be of interest. In my isolated turret I thought this was common knowledge.

The process of casting involves the poring of molten and in the case of the small mill castings into moulds made from a special sand which is imprinted with a matrix or pattern in the shape of the form to be cast. For the complex shapes as in a lathe bed or mill table there will be at least two parts to the mould. Simple shapes such a blocks of iron only require a simple depression that can be filled from the foundry ladle. Feed channels are added and vents hollowed out in the sand on what is usually the lower half and the upper half lowered into place. Further complications are added if cores are added to reduce the amount of machining - as for example the inside of the gear box on the Sieg mills. The cores are often made from sand and sugar mix that is baked in a mould and supported in the sand mentioed previously. Sounds complicated and is a bit of a black art! The real expertise is in getting the molten iron to fill the resulting cavity without bubbles. This was and I believe still is where the skill of the foundry is evident.

The casting cavity is obviously over dimensioned as the cast iron shrinks on cooling. The cooling process is controled or alowed to take place naturally with these simple castings. This leaves the resulting metal with a hard outer skin which also contains some sand to add to the first cut problems. Old hands use a blunted cutter with a generous rounded lip to remove the first layer. Normally prior to machining the castings would be fettled - the sprue caused by the feed and vent ducts reffered to above removed. The castings should then be left for a time to what the old hands called maturing which can be speeded up by heat cycling and or mechanical means such as hammering.

For precision items such as gear wheels and machine beds the 'matured' casting would then get its first machining. Care would be taken to leave sufficient metal to allow for any resulting twisting caused by the removal of the tensions in the stock that is taken away. On big castings the movement is vissible to the naked eye. A further period was then alowed for the internal stresses to stabilise before the finishing to size - grinding flat etc.

A trawl of the web will bring up some further reading material. I think I have given you enough detail to see the sort of problems taht aris. Obviously having a big delay between machining operations is not compatible with low cost production. Whilst casting techniques have progressed this is still a problem particularly for low cost foundry work. This link is worth a look http://www.sawmillcreek.org/showthread.php?t=19751 as is any text book on machining castings.

Thus with some of the major surgery undertaken to install ball screws may not be a good idea. Correcting any twists that might be induced would require some serious scraping using the three flats method to bring the surface back flat. In the context of the slides on a machine there is the issue of having the mating surfaces aglined as well as flat. Again text books should be consulted on the three flats process as it is not a trade secret just the sort of boring work handed out to the youngsters to do under the watchful eye of the old hands!

Hope this satisfies - good luck.